This invention was made in the performance of a Cooperative Research and Development Agreement with the Department of the Air Force. The Government of the United States has certain rights to use the invention.
The present invention relates generally to aircraft control systems, and more specifically, to a wing mounted aircraft yaw control device for imparting yaw moment to tailless aircraft.
The advantages of all-wing, tailless aircraft are known. For example, tailless aircraft provide enhanced stealthy operating characteristics due to their inherent low-observable configuration. Moreover, all-wing aircraft provide other benefits such as improved efficiency due to reduced weight and drag and, accordingly, are well suited for use in a wide variety of applications such as in remotely controlled aircraft. An example of a successful all-wing tailless aircraft in use today is the B-2 Spirit aircraft employed by the U. S. Air Force.
A significant disadvantage of the tailless aircraft configuration lies in the attendant loss of the aircraft rudder normally incorporated within the vertical tail section. The rudder is provided in conventional aircraft to provide side to side or yaw moment to the aircraft in flight. Therefore, with the loss of the rudder, other means must be provided to impart yaw moment to the tailless aircraft.
The B-2 Spirit aircraft cited above overcomes the loss of the rudder by the incorporation of what is known as a split aileron at the trailing edge of the wing. The split aileron operates in xe2x80x9cclamshellxe2x80x9d fashion, opening when necessary to provide increased drag and hence impart yaw motion to the aircraft. While this technique works quite well and overcomes the loss of the rudder on the aircraft, it has inherent limitations associated with it. For example, the operating moment forces imparted on the split aileron actuator during operation are quite large. This necessitates the application of large forces and a concurrent expenditure of large amounts of energy in order to effect the desired yaw moment during flight. The control mechanism must be similarly large, disadvantageously adding to aircraft weight.
Another limitation inherent in this design is that there exists a xe2x80x9cdeadbandxe2x80x9d of actuation wherein the ailerons must be deployed a minimum amount before any yaw motion takes place. This is due, in part, to the placement of the ailerons on the trailing edge of the wing. As a result, the ailerons are often maintained in a partially extended position in order to reduce the deadband effect. This has the disadvantage of increasing drag as well as forces exerted on the aileron extension mechanism.
A need exists for an improved wing mounted yaw control device for tailless jod aircraft. Such a device would provide improved yaw control characteristics while requiring low actuation forces and minimize aircraft drag in order to impart the desired yaw moment to an aircraft in flight.
It is therefore a primary object of the present invention to provide a wing mounted yaw control device overcoming the limitations and disadvantages of the prior art.
It is another object of the present invention to provide a wing mounted yaw control device that provides effective yaw moment to a tailless aircraft in flight.
It is yet another object of the present invention to provide a wing mounted yaw control device requiring relatively low actuation forces during operation.
These and other objects of the invention will become apparent as the description of the representative embodiments proceeds.
In accordance with the foregoing principles and objects of the present invention, a wing mounted yaw control device is provided to impart yaw motion to an aircraft in flight. The wing mounted yaw control device of the present invention has particular utility on tailless aircraft in order to compensate for the loss of the vertical rudder found on conventional aircraft.
The wing mounted yaw control device of the present invention includes a deployable spoiler hingedly mounted on the upper surface of the aircraft wing. A deployable deflector is hingedly mounted on the lower surface of the aircraft wing. A deployment mechanism is mounted within the wing and is provided to effect the simultaneous deployment of the spoiler and deflector. The spoiler and deflector, when deployed, impart a net drag force to the wing. This, in turn, causes a yaw moment to be imparted to the aircraft due to the unbalanced drag force on the one wing, causing the aircraft to move in the yaw direction. The degree to which the spoiler and deflector are deployed corresponds with the degree of yaw moment imparted to the aircraft. Thus, gradual turns can be readily effected by selective partial deployment of the spoiler and deflector. Moreover, it can be appreciated that the wing mounted yaw control device of the present invention can also provide an effective speed brake when deployed on both wings simultaneously.
Advantageously, the operative combination of the spoiler and deflector requires very low actuator force during operation. This is because the spoiler tends to direct the airflow away from the wing while the deflector tends to direct the airflow into the wing. The net effect is to achieve a balance between the closing force imparted to the deployment mechanism by the spoiler and the opening force imparted to the deployment mechanism by the deflector. In this way, a low or even zero net torsional moment is created. Moreover, it should be appreciated that this force balancing effect is found throughout the operating range of the wing mounted yaw control device of the present invention. This has the dual advantage of providing ease of operation while simultaneously reducing the size and energy requirement of the deployment mechanism.
As can be seen, the wing mounted yaw control device of the present invention imparts the desired yaw moment to an aircraft in flight while requiring the input of low actuation forces. The wing mounted yaw control device provides effective aircraft yaw moment throughout the range of aircraft operation while requiring very low actuation force.